Chimney draft device.



E. PRAT.

CHIMNEY DRAFT DEVICE.

APPLICATION man 11m29.191s.

2 SHEETS-SHEET l.

i @as E. PRAT.

CHliVINEY DRAFT DEVICE.

APPLICATION FILED Amma, 1913.

915196@ Mmmm. SI, m5.

2 SHEETS-SHEET 2.

rn semaine refr annie.

EMILE PRAT, OF PARIS. FRANCE, ASSIGNOR TO LOUIS PIAT, OF PARIS, FRANCE.

CHIMNEY ERAFT DEVICE.

Application filed August 29, 1913.

T0 all whom it may concern:

Be it known that I, EMILE IIwr, a citizen of the French Republic, residing at laris, in the Republic of France, have invented certain new and useful Improvements in Chimney Draft Devices; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

My invention relates to an arrangement for automatically controlling furnaces, more particularly boiler furnaces, by means of simultaneous induced and forced draft. For this purpose I employ a single blowing device comprising one or more blowers, provided with one and the same discharge duct which is divided into two conduits having a controlling member common to both for varying the ratio of the quantities of air forced through them. When the pressure of the forced draft under the furnace grate increases, the partial vacuum of the induced draft decreases, and vice versa, a constant pressure being thus maintained in the furnace.

In the accompanying drawings, which illustrate examples of arrangements for carrying out the invention, Figure 1 is a diagrammatic view showing the general arrangement Vof a boiler with its flues and the apparatus for regulating the draft. Fig. 2 is a partial view showing a similar arrangement provided with a heater.

In the exhaust-Hue' a, leading the gases from the boiler Z) to the chimney c, is placed an air-blast nozzle d, which is connected by a pipe e to a blower f situated outside the circuit, in the well-known manner. The outlet g of the blower is also connected by a pipe z, leading to the passage z' whereby the air is delivered to the grate of the furnace. At the bifurcation of the pipes e and h is placed a valve 7c connected to a piston m (or iiexible membrane) which is exposed Von one face to a substantially constant pressure, preferably that of the atmosphere, and on the other face to a pressure derived, through a pipe n, from the contracted portion of a vacuum-multiplier 0, of the Bourdon type, which is placed within the pipe 71, or connected with said pipe in any 'convenient manner. Equilibrium between the pressures on the opposite faces of the piston m is maintained by means of a spring p or a counterweight..

Specification of Letters Patent.

Patented Aug. 3i, 19315.

Serial No. 787,315.

Instead of a piston or membrane m there may obviously be employed any equivalent device operated by pressure-diflerences, such for example as a mercury-float; and instead of a vacuum-multiplier there may similarly be employed any device capable of respondlng to variations in the rate of flow, for eX- ample a Pitot tube. The connection between these two devices may be maintained through the medium of a servo-motor or of a suitable form of relay.

The operation is as follows: In normal working, the blower f' delivers through the pipe za portion of the air which it discharges, so as to feed the grate j; while another portion of the air, in the desired ratio relatively to the first-mentioned portion, is blown by the nozzle Z into the lower end of the chimney c so as to produce a partial vacuum therein and thus cause the gases to be drawn out of the furnace. The Valve le placed between the two pipes e and h then occupies the position indicated in full lines Vin the drawing, which position is determined by the action exercised upon it by the piston m in consequence of the rate of flow existing in the passage' z'. If the resistance within the furnace increases, for example if the grate has just been charged with fuel, the rate of flow in the circuit tends to decrease. T he partial vacuum at the constriction of-the vacuum-multiplier o being thus diminished, the piston lm, descends and raises the valve 7c to the position shown in dotted lines. If under these conditions the valve la remained stationary, the partial vacuum in the chimney at the mouth of the nozzle al would not vary. The flow having decreased in the yconduit j b a c, the loss of pressure in said conduit, that is to say the difference between the pressure in the furnace and the pressure at the mouth of the nozzle, would be smaller than in normal working. Therefore the pressure in the furnace would fall under atmospheric pressure, assuming that it was atmospheric pressure in normal working. This will be better understood by a numerical example. Assuming for instance that in normal Working the gage pressure be 0 in the furnace, the partial vacuum being minus l inch at Z and the loss of pressure being l inch between these two points. After having charged the grate with fuel the loss of pressure is reduced to inch; if the partial vacuum had remained minus 1 inch at d, a partial vacuum of minus i inch would` `be produced in the furnace.

The advantages are as follows: Owing to.

the fact of the pressure being regulated at two points in the circuit simultaneously, the

sensitiveness and the precision of the regulation are very great. As soon as the resistance in the circuit varies, the effect is manifested in the device which is subject to the influence of the rate of flow. By suitably proportioning the movements of the valve c it is possible to obtain, under any conditions of working, atmospheric pressure above the bed of fuel. The two actions, that of increase of pressure beneath the grate and that of diminution of partial vacuum in the chimney, or inversely, operate in the same sense so as to give this result. Hence it is possible to open the furnace-doors with impunity, and there will be no entry of air. Nevertheless, it is advisable to keep the furnace undera slight degree of vacuum so that there shall be no escape of flame when fresh fuel is thrown upon the grate. There already exist other arrangements directed to obtaining atmospheric pressure in the furnace, and utilizing for this purpose the pressure which exists within the furnace. These arrangements have the disadvantage that their operation is not rapid and precise, for the reason that it depends upon the variations of pressure in the furnace, which it should be the aim to avoid. Furthermore, it is to be observed that the arrangement of the present invention permits the use of a single damper for regulating at once both the forced and the induced draft, whereas in the other arrangements there is one damper for the air-supply and another for the exhaust of the furnace gases. Again the invention offers the further advantage that when the resistance in the circuit of air and gases increases, for instance when the grate has been freshly charged with fuel, the useful work performed by the total amount of combustion and suction air is increased, without the necessity of increasing the work of the blower, for the following reason: The total amount of air discharged by the blower is divided into two portions in the conduits i and e. The portion flowing through i operates the transport of the combustion gases without any appreciable loss of work because it blows direct under the grate; the portion flowing through e, however, acts on the combustion gases by suction by means of the nozzle al, and it is a known fact that such a suction takes place with a small useful effect. Then the grate is freshly charged, the work performed by the former portion of air operating with a high useful effect increases, and the work performed by the latter portion of air operating with a low useful effect diminishes; the useful effect of the total amount of air therefore augments, while the work of the blower may remain invariable. i

Instead of a single blower, several blowers may be employed, in particular two blowers mounted on the same shaft, as it is only essential for the invention that the blowing apparatus should have one and the same delivery conduit g divided into two conduits l1. and 0.

W hen the invention is used in connection with a boiler furnace, the steam pressure being liable to var)` in the boiler, the above described arrangement may be combined with a device forregulating the operation of the blower by the said steam pressure. The steam-pressure may operate, for example., through the medium of the steam conveyed by a branch-pipe l] to a cylinder r wherein works a piston t subject to the pressure of a spring s of any kind. The movements of the piston, produced by the variations of steam-pressure, are transmitted either toa valve or obtuator u serving as a means of regulating the admission of steam to the motor which drives the blower, or to any kind of regulating device (electric for example) if the blower be not driven by a steam-engine. By this means, to each pressure in the boiler there corresponds a different speed of the blower, dependent solely on such pressure. On the other hand` at each speed the blower regulates the draft independently of the boiler-pressure.

lf desired, the air delivered by the pipelz., instead of being led directly to the grate, may first be caused to pass through a heater 'n placed in the path of the furnace-gases (see Fig. 2).

The arrangements described may obviously be considerably modified to suit the character of the installation to which they are applied or the particular form of apparatus adopted.

The invention is applicable not only to steam-generators, but also to furnaces of various types and to ovens of all sorts. lt has been illustrated in combination With one particular type of consti-action but is capable of being applied to any system of draftcontrol.

What I claim is:

1. Apparatus of the class described comprising a combustion chamber and an exit flue therefor; in combination with blowing apparatus having a single outlet, branch conduits leading from said outlet, one to a point under said combustion chamber and the other into said exit flue in a direction marmi to aid the draft therein, a single controlling device near the point of separation of said conduits, adapted to control the relative proportion of air supply to the same, and automatic means controlled by air pressure for operating said controlling device, substantially as described.

2. Apparatus of the class described comprising a combustion chamber and an exit Hue therefor; in combination with blowing apparatus having a single outlet, branch conduits leading from said outlet, one to a pointt under said combustion chamber and the other into said exit Hue in a direction to aid the draft therein, a damper atthe point of separation of said conduits arranged to be capable of swinging across either conduit at will, and automatic means for swinging said damper, substantially as described.

3. Apparatus of the class described comprising a combustion chamber and an exit Hue therefor; in combination with blowing apparatus having a single outlet, branch conduits leading from said outlet, one to a point under said combustion chamber and the other into said exit Hue in a direction to aid the draft therein, means for oppositely affecting the currents in said branch conduits simultaneously, and independent automatic means for controlling the output of said blowing apparatus, substantially as described.

4. Apparatus of the class described comprising a combustion chamber and an eXit Hue therefor; in combination with blowing apparatus having a single outlet, branch conduits leading from said outlet, one to a point under said combustion chamber and the other into said eXit Hue in a direction to aid the draft therein, a controlling member common to said branch conduits, and a device responsive to the How of Huid in the circuit of air and gases for operating said controlling member.

5. Apparatus of the class described comprising a boiler, a combustion chamber, and an exit Hue therefor; in combination with a blowing apparatus, branch conduits leading one from the same to a point under sai combustion chamber and the other into said exit Hue in a direction to aid the draft therein, a controlling member common to both branch conduits, a device responsive to the How of Huid in the circuit of air and gases for operating said controlling member,

. and means responsive `to the steam pressure in said boiler for controlling said blowing apparatus, substantially as described.

- 6. In a device of the class described, a combustion chamber, an eXit Hue therefor, a blower and branch conduits leading one from said blower under said combustion chamber and the other into said exit Hue in a direction to aid the draft therein; in combination with governing means for varying the relative proportions of draft in said branch conduits, a controlling device, responsive to opposed Huid pressures, adapted to control the position of said governing means, and means 1n one of said branch condults, responsive to changes of draft therein, adapted to determine the balance of Huid pressures in said controlling device, substantially as described.

ln testimony whereof, l aHix my signature, in presence of two witnesses.

EMLE PRAT. Witnesses:

Luci-EN MEMMINGER, ALBERT NUNES. 

